Caseless cartridges



Aug. 27, 1968 R; c. KvAvLE 3,398,684

CASELESS CARTRIDGES Filed June 28, 196e I M1@ Z Inventor Fobrf' CvavZeje his Attorney Safes, Patent :O

,ABsTRAmi oF Tina DIscLosURE Vpiojectile houses in its rear end apropellant charge comprised primarily of solidlow explosiveprefe'rably'in 'the form'of nitrocellulose 'breshaving air'in 'their tsub-`s'tant'iallyl interconectedffin'terstitial spaces, the charge liaviigfadensityless than that of nitrocellulose per se. While -ignitionmay'be''effected:electrically or otherwise, one mode of ignitioncontemplated for the cartridge is that eifected by impat withlthec'ha'rge in a substantially closed chamber sealed bythe projectile.

A copending application, 3L/ 1,242 tiled May 29,

1964, in my name, now Patent 3,283,657 discloses a novel method andmeans for initiating deagration in a solid low explosiveythe 4requiredheat beingffrictionallyfgenerated solely by impacting the charge in asubstantially closed chamber. This procedure does not rely upon raisingtemperature by precompression of air about the charge. In anothercopending application Ser. No. 524,168, tiled Feb. 1, 1966, in my name,there is described a formed low explosive charge of brous nitrocellulosefor use in impact ignition devices operable in the novel mannerindicated.

A primary object of the present invention is to provide a caselesscartridge carrying within its breech end a solid, stable, impactignitable charge of low explosive propellant.

A further object is to provide a relatively safe, low cost combinationprojectile and solid propellant adapted to be operated by impactignition in a chamber sealed by the projectile itself and its own tiringmechanism. Another object is to provide a light weight projectile havingno cartridge case requiring extraction.

To these ends, and in accordance with a feature of the invention, thereis contemplated a projectile having its breech end formed with tacharge-containing cavity, the walls and bottom of the cavity being linedwith solid low explosive, and a portion of the explosive lining,preferably the bottom wall, being adapted to be impact ignited toinitiate deagration and hence gas propulsion of the projectile. Afurther feature of the invention resides in the provision, in a caselesscartridge of the type indicated, of means such as an external sealingring or other obturating means, for instance fins, for providing initialresistance to relative movement of the projectile with respect to thering mechanism, the tins being radially deflectable or deformable inresponse to pressural build-up in the ring chamber to permitacceleration of the projectile. Since as heretofore noted, ignition ofthe projectile is to occur in a chamber sealed in part by itself, it iscontemplated that a limited air volume surrounding the breech end of theprojectile may be predetcrminedly entrapped during ignition by a bolt inthe firing chamber and a relatively movable firing pin adapted to enterthe projectile cavity to impact its bottom or deagratable lining.The,air volume permitted by the projectile, bolt, and pin ispredeterm'1nedly small and hence there is practically no energy wastedin raising its temperature by compression, substantially all kineticenergy of the pin being used to .compress and frictionally crush atleast a portion of the propelling charge being Lignited. i I

' The foregoing and other features of the invention, together with noveldetails in construction, will nowbe more particularly describedinconnection with ankillus.- trfative embodiment and with reference to theaccompanying drawings thereof, in which; i FIG. 1 is a view inside.elevation of a caseless cartridge 1n accordance with this invention andincluding a projectile loaded into the firing position of a barrel borehaving ring mechanism including a bolt and ring pin; 4

FIG. 2.is adetail Yshowing the tiring pin striking the projectilecharge;

.FIG 3 is a view corresponding to FIG. l, the projectile beingl shown inaxial section at the instant of impact 1gn1t1on;

FIG. 4 is an enlarged perspective view of the breech end of theprojectile of FIGS. 1 and 3 after it has been red and indicating itsannular sealing ring as deformed by the barrel rifiing; y

FIG. 5 isa detail view in perspective similarto FIG. 4 but showinganother projectile retaining means in the form of groove tting ribs; and

FIG. 6 is a view corresponding to FIG. 5 and showing the retaining ribsas radially deformed in consequence of dellagration of charge.

Referring to FIGS. 1 and 2 a projectile having a cylindrical body 10 maybe of any preferred external configuration, its muzzle end generallybeing pointed and its breech end 12 formed with a cavity 14. This cavityis usually, though not necessarily, cylindrical and coaxial with thebody 10. No separate case is needed for the projectile since its cavity14 is adapted to receive and internally store its charge 16 of solid,low explosive.

The charge 16 may itself be of different low explosive materials andshapes but it preferably lines the bottom and walls of the cavity 14, aportion at the cavity bottom having a raised, reduced area 18 (FIG. 2)to be initially impuacted to effect ignition, for instance by a firingpin 20 moving axially to crush at least a part of the charge and thusfrictionally generate the heat for ignition which thereafter causes theentire charge progressively to deflagrate.

As disclosed in the application Serial No. 524,168, cited above, onecharge which may be formed Within the body 10 or separately formed as apellet and then inserted at the time of imminent use, comprisescompacted brous nitrocellulose powder. It may include a stabilizerand/or coloring agent, and desirably has a density of less than 1.6 gms.per cc. While the range of propellant density may vary, a density of-about l gram per cc. is usually preferred for funiform, reliableperformance. The porosity of such a charge when molded intoself-sustaining shape and having entrapped air is believed to facilitateinitial ignition by reason of the heat from friction generated duringcrushing action. Ignition is facilitated by reason of the ribbonlikefibres dening substantially continuous interstitial burning surfaces.

As disclosed in the above-mentioned applications, no detonation isinitially produced, but deilagration is -achieved in the solid, lowexplosive with the expenditure of a relatively small amount of energy byspot heating it electrically or by imp-acting consequent build-up inpressure leading to detonation. This manner of safely and effectivelygenerating propellant gases from the charge is practiced in a closed orsubstantially closed chamber 24 one end of which is sealed in a barrel26 by the breech end of the projectile, and the other end of the chambermay be sealed by firing mechanism, for example a bolt 28' and the pin 20reciprocable therein. For the purpose of holding the projectile againstaxial displacement in the barrel at the instant of firing pin impact onthe charge 16, the breech end 12 preferably is provided with restrainingmeans such as an external sealing ring 30l (FIGS. 1, 3, and 4) adaptedto engage the wall of the chamber 24 at the end of bore ritiing 32. Asindicated in FIGS. 5 and 6, another form of restraining means may becircumferentially spaced lugs 34 adapted initially to preventdisplacement of the projectile as by interference initially with thebarrel bore, but upon build-up of pressural 4gases in the chamber 24, beradially deformed or sheared off to permit projectile flight. FIG. 4indicates how the ring 30 may be slotted as at 36- by the riing 32'following ignition and completed combustion of the charge 16. Numerousother sealing iins and shrouds are known or may be devised for use withthe projectile, or as an integral part thereof, to restrain it duringimpact ignition and insure that it will receive the benefit of electiveobturation.

It is unnecessary that the pin 20l closely t the hollow within thecharge 16. The volume of the latter is selected to provide the degree ofprojectile velocity required. Only a short firing stroke of the pin 20is needed. The volume of the iiring chamber 24 is mainly determined fora charge size by ixedly positioning the adjacent end of the Sealingbolt. Upon impact of the pin 20 with the igniter portion 18, the initialrestraining means 30l or 34, for instance, insure that the projectilewill have its charge 16 deagrated. The gases of combustion increasetheir pressure in the chamber 24 as deiiagration accelerates in thecavity l14. Accordingly, in a very short time the sealing ring 30 orother equivalent can no longer restrain the projectile which then israpidly propelled from the barrel. Means (not shown) is of courseprovided for preventing blow-back of the pin 20l and the bolt 28.

Having thus described my invention, what I claim as new and desire tosecure by Letters lfate'r1tV of flie'Unitd States is:

1. A caseless cartridge comprising a projectile body having a breech endformed-,with a cavity, and a solid, low explosive propellant, k'lining-at least a portion of the cavity, said explosive being mainly of nitrocelluloseviibres having a density less than that of nitrocelluloseAperfse, the iibres defining substantially. continuous interstitialburning surfaces.

2. A primerless cartridge asset forth in claim 1 wherein the lowexplosive propellantnis fibrous nitrocellulose powder compacted to adensity of about one gram per cc.

3l. A cartridge asset forth `'in claim 2 wherein the lining of lowexplosive is cylindrical, tubular, and has a diameter less than itsaxial length, Y

4. A primerless cartridge as sethforth in claim 1 wherein said cavity iscoaxial with the projectile body, andthe propellant at the bottom of thecavity has a centrally raised, reduced area adapted to facilitateignition.

References Cited UNITEDY STATES PATENTSv 5,701 8/1848 Hunt 10Q-49.340,092 9/ 1863 Dibble 102--49.3 552,919 1/1896 Maxim 102--101 1,243,25310/1917 Bush 102-40 2,307,369 1/ 1943 Ferrel. 2,407,264 9/ 1946 Ferrel.3,311,057 3/1967 Quinlan et al. 102-38 OTHER REFERENCES MilitaryPyrotechnic Series, Part Three, Properties of Materials used inPyrotechnic Compositions, U.S. Army Material Command, A.M.C.P. No.106-187, pp. 218-- 220, October 1963.

ROBERT F. STAHL, Primary Examiner.

